Re: Record operations (Algebraic Data Types and printing)

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On 2018-10-10 00:20, Randy Brukardt wrote:
> "Lucretia" <laguest9000@googlemail.com> wrote in message
> news:fb2af9cb-5317-4f1c-867c-8876212d303b@googlegroups.com...

>> Like what 'Read/'Write/'Input/'Output do, they call a defined subprogram in
>> the package. Surely, it's not that hard.
> 
> What package? We're talking about (in part) the default representation for a
> type.

What have T'Image and T'Value to do with the type representation?

> Stream attributes use a complex concept called "availability" to deal
> with limited types, and they don't worry about privacy breakage at all.

Limited types should have no stream attributes at all. Same applied to 
'Image/'Value. Returning limited object was a language design bug. This 
cannot be fixed but it can be contained.

> 'Value would need something similar at a minimum, and the question of
> privacy breakage also would have to be addressed (a package would not want
> some outside force constructing values for its types; they might not meet
> the [implied] invariants and other assumptions

[...]

Safe default is to generate publicly visible 'Image and 'Value 
propagating Use_Error for all types with private components. The package 
provider could override them in the public part with bodies renaming the 
private default implementations of which have full visibility.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de